Rename #rs_export_reduce_new to #rs_export_reduce.

This brings general reduction metadata into conformance with the
specification and removes simple reduction metadata, thereby
disabling simple reduction.  More work will be done later to
fully remove the simple reduction implementation.

Requires a corresponding change in frameworks/compile/slang.

Bug: 23535724
Change-Id: I7effa0ab1cd4ecd75f32e0c8509a737cfbb52dbd